But in the real world monitoring is not costless and information and enforcement
are not perfect. A standard of efficiency impossible to achieve in the
real world is not a useful test against which to define market failure. The test
of efficiency should still be that a Pareto improvement is impossible to find,
but such an improvemenmt ustb e soughtt akingi nto accountt he imperfections
of informationa nd enforcementh at the marketi n questionh as to deal withthat
is using the concepto f constrainedP aretoe fficiency.B y this standard,t he
outcome described above, where the lender reduced the amount lent to a borrower
because of monitoring difficulties, could in fact be efficient in a constrained
sense. The information problem may still have an efficiency cost to
society, but from an operationalp oint of view that cost has no relevance